1. Field of the Invention
The present invention generally relates to electric and hybrid vehicles with a regeneration mode, and is particularly concerned with a regeneration mode actuator and indicator system and method for such vehicles.
2. Related Art
Various braking systems and indicators for such systems are known for various types of vehicle, including traditional gas driven vehicles, hybrid vehicles, and electric vehicles. One problem with existing brake lights is that they are only turned on when the driver applies conventional friction brakes. They are not activated when the vehicle slows down for some other reason.
An electric or hybrid vehicle automatically switches into a regeneration mode periodically as controlled by the electronic control unit (ECU) based on detected vehicle conditions, but the driver can also initiate regeneration either by applying the brakes or shifting the vehicle into low gear. Drivers of electric or hybrid vehicles sometimes shift the vehicle into low gear to slow the vehicle while increasing efficiency by delivering power to the storage battery of the vehicle. However, a driver following a conventional hybrid or electric vehicle which is operating in regenerative mode without conventional brake application has no indication that the vehicle is decelerating.
Some prior vehicle indicators are designed to be actuated on detection of slowing of a vehicle resulting from either traditional friction braking or other types of deceleration, for example due to gear shifting. However, these systems do not discriminate between slowing as a result of applying conventional vehicle brakes and slowing for other reasons, for example as a result of initiation of the regeneration mode in a hybrid or electric vehicle.
Electric vehicles are designed to mimic the slowing that occurs in gasoline powered vehicles with an automatic transmission. In electric vehicles, the drive gear slowing sensation (referred to as leakage) and low gear slowing (measured and speed dependent) are exclusively done with the regenerator. In the case of low gear, the regenerator is taken close to saturation or maximum output of the regenerator. An additional slowing, intentional or not, reduces the kinetic recovery potential and thus the overall efficiency of the vehicle.
Driving an electric vehicle in low gear is unofficially stated as an option by manufacturers. The problem with this mode of electric vehicle use is that the efficiency of just coasting above leakage at all times when not accelerating is continuously reduced by the slowing of low gear, and encounters the unnecessary inefficiencies of the kinetic conversion to electric power. Vehicle operators with regenerators are not encouraged to maximize the regeneration feature with modulation of the brake pedal. A brake pedal that utilizes regeneration does so in conjunction with conventional braking. The operator experience is intentionally seamless. That is, the primary consideration is stopping with an expected vehicle slowing feedback to the operator. This offers some kinetic recovery efficiency, but normally involves unnecessary application of conventional frictional brakes.